Vulnerability in Pre-Installed App Allows Arbitrary AT Commands Execution

Summary

Certain software builds for the Nokia C200 and Nokia C100 Android devices contain a vulnerable, pre-installed app with a package name of com.tracfone.tfstatus (versionCode='31', versionName='12') that allows local third-party apps to execute arbitrary AT commands in its context (radio user) via AT command injection due to inadequate access control and inadequate input filtering. No permissions or special privileges are necessary to exploit the vulnerability in the com.tracfone.tfstatus app. No user interaction is required beyond installing and running a third-party app. The software build fingerprints for each confirmed vulnerable device are as follows: Nokia C200 (Nokia/Drake_02US/DRK:12/SP1A.210812.016/02US_1_080:user/release-keys and Nokia/Drake_02US/DRK:12/SP1A.210812.016/02US_1_040:user/release-keys) and Nokia C100 (Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_270:user/release-keys, Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_190:user/release-keys, Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_130:user/release-keys, Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_110:user/release-keys, Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_080:user/release-keys, and Nokia/DrakeLite_02US/DKT:12/SP1A.210812.016/02US_1_050:user/release-keys). This malicious app sends a broadcast Intent to the receiver component named com.tracfone.tfstatus/.TFStatus. This broadcast receiver extracts a string from the Intent and uses it as an extra when it starts the com.tracfone.tfstatus/.TFStatusActivity activity component which uses the externally controlled string as an input to execute an AT command. There are two different injection techniques to successfully inject arbitrary AT commands to execute.